The New Standard In Dwell Times

This is the first part of a three-part article about dwell times.

When disinfecting high-touch areas, janitors know the drill on dwell times: In order to do its job effectively, a disinfectant should remain on the surface for the manufacturer’s recommended contact time — in many cases a standard dwell time of 10 minutes. But building service contractors are also aware that a 10-minute contact time is often impractical, and janitors are less likely to adhere to it when pressed for time.

“The only way an institution can achieve a contact time of 10 minutes is to reapply that disinfectant five or six times, because it usually dries in a minute and a half to two minutes,” says Darrel Hicks, author of “Infection Prevention for Dummies” and owner of Darrel Hicks LLC, St. Charles, Missouri. “That’s just unfathomable: With today’s productivity expectations, employees don’t have time to watch the surface dry and then rewet it six times.”

Benjamin Tanner, president of the Antimicrobial Test Laboratory in Round Rock, Texas, estimates that only 5 to 10 percent of users apply disinfectant such that the surface stays saturated for 10 minutes.

“When we test disinfectant in a lab, we spray it with a trigger sprayer three to five times from a distance of about 6 inches, at a 45 degree angle, into a Petri dish containing a glass slide inoculated with organisms,” he says. “There’s no problem with evaporation in a laboratory. It’s generally wet for 10 minutes and will probably be wet for 30 minutes. In real life though, things are used much differently. In reality, people spray it and wipe, then spray it again and maybe wait for 30 seconds before wiping.”

Even in a perfect world where janitors apply the disinfectant so that it remains on the surface a full 10 minutes, other factors come into play that could jeopardize the disinfection process.

“We’ve always looked at seven to 10 minutes as being standard, but whether or not that’s totally effective is another question,” says Bill Griffin, president of Cleaning Consultant Services Inc. in Seattle. “You need to look at how much soil is on the surface. Are you cleaning first and disinfecting second? Did the person dilute and mix the product properly? All these things come into play. So you cannot take a standard of 10 minutes anymore and use that, because it doesn’t apply to everything. That’s an old standard.”